The accessory Sec system of Streptococcus gordonii is essential for transport of the glycoprotein GspB to the bacterial cell surface. A key component of this dedicated transport system is SecA2. The SecA2 proteins of streptococci and staphylococci are paralogues of SecA and are presumed to have an analogous role in protein transport, but they may be specifically adapted for the transport of large, serine-rich glycoproteins. We used a combination of genetic and biochemical methods to assess whether the S. gordonii SecA2 functions similarly to SecA. Although mutational analyses demonstrated that conserved amino acids are essential for the function of SecA2, replacing such residues in one of two nucleotide binding folds had only minor effects on SecA2 function. SecA2-mediated transport is highly sensitive to azide, as is SecA-mediated transport. Comparison of the S. gordonii SecA and SecA2 proteins in vitro revealed that SecA2 can hydrolyze ATP at a rate similar to that of SecA and is comparably sensitive to azide but that the biochemical properties of these enzymes are subtly different. That is, SecA2 has a lower solubility in aqueous solutions and requires higher Mg(2+) concentrations for maximal activity. In spite of the high degree of similarity between the S. gordonii paralogues, analysis of SecA-SecA2 chimeras indicates that the domains are not readily interchangeable. This suggests that specific, unique contacts between SecA2 and other components of the accessory Sec system may preclude cross-functioning with the canonical Sec system.

BACKGROUND

Endoscopic necrosectomy is now an established minimally invasive method for treatment of organized pancreatic necrosis.

METHODS

Review of methods and results of endoscopic treatment of pancreatic necrosis.

RESULTS

Reports by multiple groups have demonstrated favorable results of endoscopic necrosectomy. The mortality of critically ill patients undergoing endoscopic treatment in several series is approximately 10%. Some patients will eventually also require surgery for situations such as complete pancreatic duct disruption, but even in these cases endoscopic necrosectomy is useful because pancreatic surgery can often be delayed until the patient is stable.

CONCLUSIONS

Endoscopic necrosectomy will likely assume an increasing role in the treatment of pancreatic necrosis. This should result in reduced morbidity and mortality in these critically ill patients.